1. Field
The following description relates to a semiconductor device and a method for manufacturing the same, and, for example, to a semiconductor device having a super junction structure and a method for manufacturing the same.
2. Description of Related Art
High-voltage and high-power devices are often used in power integrated circuit (IC) apparatuses for power conversion and in power control systems. A planar gate metal oxide semiconductor field effect transistor (MOSFET) is widely used as such a high-voltage device.
However, in a planar gate MOSFET, in order to maintain the distribution of electric field in its epitaxial region, a certain minimal thickness needs to be maintained in the epitaxial region, and the epitaxial region needs to have a certain minimal concentration of dopants. Thus, due to the relationship between the electric field distribution and the thickness and dopant concentration, it is difficult to obtain a MOSFET that has less than a certain resistance component. In order to solve this limitation, a super junction structure has been suggested.
The conventional super junction semiconductor device comprises components that bear some resemblance to a gate and a p-type well structure of a general MOSFET. However, the p-type pillar region for obtaining super junction characteristics is formed in an n-type pillar region at a lower end of a p-type body region. The difference in structure results in the following effect. In a general MOSFET, a depletion layer extends only in a vertical direction when a voltage is applied to its drain. In a super junction semiconductor device, a depletion layer extends in both a vertical direction and a horizontal direction when a voltage is applied to its drain. In such a device, when the quantities of charge in both regions are the same, as the n-type and p-type regions are depleted, a high breakdown voltage can be obtained. Since charge does not exist in the vertical direction, an electric field in the vertical direction is constantly generated in theory.
However, the conventional semiconductor device having the super junction structure has a problem in that, because a resistance of a drift region near a drain region is relatively higher than that of a drift region near a source region, high current density is not obtained at the time of being turned on.
Patent Literature: U.S. Pat. No. 7,345,342